Changing User note font size deletes embedded image in User notes

I open User note. There is an image embedded in the User note. 

I add a few lines below the image and add my notes. Command+A, select all text, change font size to 16 pt and image above the text disappers. Save. Image is gone. 

Luckily I had iPhone at hand so I could open the same note on iPhone, ta-p-and-hold on the image, copy image to clipboard and paste it in the user notes on my Mac. 

I think changing font face or size in the User notes shouldn't remove embedded images.